What cold corona generator would you recommend?
I build my own so I know that they are truly cold corona. And for some of the experiments I do I need a higher concentration of ozone than the commercial units put out. But one of the posters on my forum bought a Synergy machine, which was a good price and sounds like a good unit from what i have seen:
Where to get oxygen source and bubbler?
Oxygen you can get from a welding supply. All oxygen has to medical grade in the US by law. You can rent or buy a tank and you will have to buy an oxygen regulator. They do not rent regulators.
As for diffusers go to a aquarium supply and get the little, white plastic aquarium diffusers. These create pretty fine bubbles and hold up to the ozone well.